1. Field of the Disclosure
This disclosure is directed to economical systems and methods for facilitating the control of dissolution of one or more gases into a liquid with little to no external energy input.
2. Background of Related Art
Many different systems and methods, depending on application, are available for dissolving gases in liquids. Some of the main applications are in the areas of water and wastewater treatment for municipal, commercial, and industrial uses; aquaculture; ground water remediation; ecological restoration and preservation; beverage making and bottling, and agriculture. Most dissolved gas delivery methods (i.e. bubble diffusion, Venturi injection, U-tubes, Speece cones) attempt to leverage Henry's Law to achieve a high concentration of dissolved gas in the carrier stream. These typically require high flow and/or high pressure from side-stream pumping in order to achieve high rates of gas dissolution.
Higher operating pressures lead to higher gas concentrations; however, this must be balanced with higher operating costs associated with achieving higher pressures. While there are variations between existing technologies operating parameters, all technologies requiring side-stream pumping operate under the same physical laws. Generally, these technologies create a large gas/liquid interface and subject it to elevated pressures for a period of time, subsequently increasing dissolved gas concentration within the liquid. All ultimately require that the gas and the liquid be in contact at the desired pressure.
Certain technologies provide energy input into the liquid and/or gas (e.g., via pumping) to achieve desired vessel pressure. Some technologies provide energy input into the liquid, with an additional energy added, such that a venturi injector can be utilized to create a vacuum allowing the gas to enter without additional energy input from the gas source.
Through algebraic manipulation, an equation can be developed for the efficiency of any side-stream saturation device, in terms of mass/time/energy (lb/d/hp).
E=(1/694.444*((P/Kh)*(s/100))*8.34)/(1*((P+L)*2.3097)/3960/(i/100)). As seen above, this equation only considers the following: Side-stream pressure requirement (P, psi), Henry's Law Constant (Kh, L*psi/mg), Percent of Saturation Achieved (s, %), Headloss Across System (L, psi), and Pump Efficiency (I, %).
For the purposes of discussion here, oxygen will be the gas of choice. However, those skilled in the art will readily recognize the method/apparatus disclosed here can be applied to any gas/liquid dissolution combination. Supplement 1 (with reference to FIG. 8) appended hereto shows the effect of pressure on dissolved gas concentration, as per Henry's Law. The effect of side-stream pumping and associated system headloss can be seen in Supplement 2 (as shown in FIG. 9) appended hereto. Based on the listed assumptions, the maximum efficiency of these systems can be seen for various pressure drop values where a maximum possible is about 58-lb/d/hp. Reducing system pressure loss will greatly impact the overall efficiency especially at pressures below about 100-psi.
The effect of side-stream pumping and associated pump efficiencies can be seen in Supplement 3 (as shown in FIG. 10) appended hereto. Pumps are not extremely efficient and become less efficient with larger solids handling capabilities. Based on the listed assumptions, the maximum efficiency of these systems can be seen for various pressure drop values where a maximum possible is about 41-lb/d/hp, or about 30% less than theoretical (Supplement 2 as shown in FIG. 9).
Supplement 4 appended hereto shows total energy requirements, side-stream pumping plus gas generation, for various oxygen dissolution technologies and approaches, as well as that of embodiments of the system disclosed herein. As can be seen, eliminating side-stream pumping requirements reduces the overall power consumption by about 60%.
For the most part, existing technologies involve side-stream pumping and either pressurized gas sources or gas sources under vacuum. While higher operating pressures lead to higher gas concentrations, to achieve these higher pressures, higher costs are involved.
Therefore, a simplified, low cost, method for dissolving a gas into a liquid, preferably while also maintaining a particular constant flow rate of said liquid is needed. Embodiments of this disclosure can eliminate the requirement for side-stream pumping and greatly reduces operating cost of side-stream gas dissolution systems.